The New 3DS XL system improves the platform in a number of ways, but it requires a micro SD card to store games you may want to download from the eShop.
The 4GB card that comes packed-in with the system is a bit small if you're a heavy player, but Amazon has a daily deal that will help get you where you need to go.
Here are your options for storage, and these deals are pretty great:
Update: The New 3DS XL can only handle micro SD cards up to 32GB in size. We've removed the 64GB link.
That's a great deal for a whole lot of storage in your system, but act fast; these prices are only good for the next 13 hours or so (as of the time of writing.)